Dehydration azodicarboxylate

A remarkable stereospecific dehydrative alkylation of (3-disulfones was reported by Falck et al. [406] under Mitsunobu conditions (triethyl phosphine, diethyl azodicarboxylate). The synthesis of a pheromone component of the lesser tea tortrix emphasizes some of the possibilities offered by coupling this reaction with further uses of the sulfone functionality. In the present case, monodesulfonylation with lithium naphthalenide (-78°C, 5 min), in situ alkylation (-78 to 23°C, 1 h), and Li-naphthalene cleavage of the second sulfonyl group (—78°C, 5 min) yielded in a one-pot procedure a THP ether which was converted into the sought after pheromone through direct acetylation. 

One of the most widely used procedures for dehydrative coupling and cyclization reactions is the Mitsunobu reaction in which the components are treated with triphenylphosphine and diethyl azodicarboxylate (DEAD, EtOaC—N=N—COiEt). The overall equation for reaction of an alcohol 67 with an acid 68 to form the ester 69 is as shown and the active species is the zwitterionic... 

Grochowski, E., Hilton, B. D., Kupper, R. J., Michejda, C. J. Mechanism of the triphenylphosphine and diethyl azodicarboxylate induced dehydration reactions (Mitsunobu reaction). The central role of pentavalent phosphorus intermediates. J. Am. Chem. Soc. 1982,104, 6876-6877. 

Isocyanides. Ugi et at.3 investigated the synthesis of isocyanides (2) by dehydration of N-monosubstituted formamides (1) with triphenylphosphine-diethyl azodicarboxylate. In the 11 cases investigated, no isocyanide could be obtained in six of them. In the... 

Scheme 9 Dehydrative glycosylations via glycosyl oxophosphonium intermediates [26-37]. DEAD = diethyl azodicarboxylate DIAD = diisopropyl azodicarboxylate.

O-protective groups such as 11 has been successfully achieved without affecting these groups by dehydration with triphenylphosphine-diethyl azodicarboxylate-iodine a mixture of anomeric C-nucleosides (12) was usually produced [94CL265 95JAP(K)95/118268] (Scheme 4). 

There are efficient ways in which to use starting materials that have the carboxylic acid component already installed on both heteroatoms conversion to bis(silyloxy) derivatives, or simply heating with p-toluenesulfonic acid. An excellent route to mono-acylated precursors utilises mixed anhydrides. A very mild method for the dehydrative ring closure of ortfto-hydroxyarylamino-amides utilises typical Mitsunobu conditions - triphenylphosphine and diethyl azodicarboxylate. ... 

Inter and intramolecular nucleophilic displacement of alcohols with inversion by means of diethyl azodicarboxylate (DEAD)-triphenylphosphine and a nucleophile. Also dehydration, esterification of alcohols or alkylation of phenols and one step synthesis of nitriles from alcohols (see 1 st edition). 

Oxepan and other oxygen- or nitrogen-containing saturated heterocycles can be prepared in high yield by the dehydrative coupling of aamino-alcohols, using diethyl azodicarboxylate and triphenylphosphine. The synthetically useful oxepin-2,7-diones (muconic acid anhydrides) can be conveniently prepared by the oxidation of ortho-henzoquinones with w-chloroperoxybenzoic acid. °... 

Alkenes. j3-Hydroxy carboxylic acids are converted into alkenes in fair to good yield by treatment with triphenylphosphlne and diethyl azodicarboxylate (equation I). The reaction involves loss of CO2 and HaO (decarboxylative dehydration). 

Esterification.—An alternative to the well-known azodicarboxylate-PhsP esterification procedure has dimethyl mesoxalate as proton acceptor. Yields of esters of benzoic acid are quite good (50—86%), and the reaction results in complete configurational inversion of the alcohol component. Isocyanides have also been shown to be useful dehydrating reagents in this type of reaction. Esterification of acids with one equivalent of an alcohol can be achieved by prior reaction of the acid with 2-halopyridinium salts. cf. refs. 134—140). An overall conversion of amines into acetates and benzoates (Scheme 29) involves conversion... 

In 1981, Mitsunobu [60] described the extension of their method of ester preparation for the synthesis of macrolactones using a mixture of Ph3 P and diethyl azodicarboxylate (DEAD) as dehydrating agent. 

Intramolecular dehydration of 3-hydroxy carboxamides affords the corresponding p-lactams. Side reactions include elimination and formation of aziridines and oxazolidines (eq 29).The efficiency of p-lactam formation is dependent on substrate substituents (including protecting groups for the side-chain amino group) as well as on the choice of azodicarboxylate and P compound. " For example, the dipeptide (33) reacts with DEAD and TPP to give a 2 1 mixture of the p-lactams (34a) and (34b). Control of the labile C-5 stereocenter can be achieved by use oi Triethyl Phosphite instead of TPP (34a) and (34b) are obtained in a >50 1 ratio (eq 30). 3-Hydroxy 0-alkylhydroxamates can also be converted into the corresponding p-lactams (eq 31). ... 

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